10/25/95
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''703 620 0913
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--.' TME INTRODUCTION OF PACK-T SATELLITE COMMUNICATIONS
Robert E. Kahn
Advanced Research
Abstract
The preparations which led to the SATNET
xeriment are discussed in this paper. Various
packet satellite tariff considerations and
architectural issues are presented along with a
smmary of future plans for use of the technology.
1. Introduction
This paper reviews the process' which led to the
introduction of packet stellite technology in the
970s, The development of this technology was
undertaken by the Advanced Research Projects
Agency (ARPA) in order to evaluate its utility for
efficient long haul computer communications with a
potentially large number of geographically
distributed users. TBis effort was undertaken in
conjumctioq with participatimg organizations in
the O.K. and.Norway, but does not necessarily
reflect their ¾1ewa on this subject.
The%most notable example of this technology is the
Atlantic Packet atellite Network, known as
SATNET, which has been in operation on the
Atlantic Intelsat IV satellite since late 1975 and
which currently serves a community of researchers
in the U.S, the O.K. and Nory. Underlying the
SATNET technologF is the basic packet switching
technology which wa first introduced during the
late 1960's. The November 1978 IE Proceedings
contains a comprehensive treatment of packet
communications technology and includes a paper on
General Purpose acket Satellite Networks which
provides a good introduction to the subject [I,2].'
SATNT consists of a__i.ng_e bad%ast channel
shared by multiple er%h tions w'nlch use Time
Di¾ieion Multiple Access (TDMA) and emit packets
according to a channel access protocol. Tese
earth stations may be connected to one or more
aubsoribem nctwor.. Eeh earth station contains
& prorable satellite processor (a controller
and related electronics) ich implements the
satellite channel protocols and interfaces. The
system provides complete connectivity between all
the participatin& earth stations and allows
dynamic allocation of the satellite channel amens
them. Different priority levels ma be supported
efficiently on the same channel without
unnecessary preallocation or preemption of
Projects Aency
resources. Tc broadcast property of the channel
enables a transmission from one earth station to
be received by 811 the others including itself.
Both conferencing and delivery of multiple address
packet ca be achieved efficiently as a result.
The Arpanet was the first example oF a packet
switched network which used point-to-point
terrestrial lines (across the U.S.) in a store anJ
forward sFstem [3,]. Following the installation
of the first Arpanet nodes, a number of papers
appeared in the literature on the application of
packet switching to multiple access radio'channels
[5,6,7,8]. The ARPA-sponsored effort at the
University of Hawaii wes the first to emonstrate
burst transmission oF packeLs by radio for
computer access by terminals within line of sight
of the computer center. In this system, called
the ALOM system [9,10], packets were simply
transmitted when they were ready to send - at
random instants of time. No explicit control of
the radio channel was invoked. Rather, o
occasion, packets would collide in the air,
destroying each other and would be retransmitted
t a later random time. The multiple access
nature of this system resemble a packet satellite
net, except that the terminals were much closer to
and quite unequally spaced from the computer
center which (like a satellite) formed the hub of
the system. The Hawaii researchers extended the
concept of radio packets to satellite
communication directly, and experimentally
verified the concept using test packets over
NASA's ATS-I satellite between Hawaii and
NASA-Ames. The technique of operating a Packet
Satellite Net in an uncontrolled fashion became
kno aS "Pure Aloha".
A significant body of theoretical wor on the
analysis of Aloha Systems appeared in te
literature in the early 1970's and various
improvements on the original random transmission
technique were proposed and evaluated [11,12]. In
the Slotted Aloha technique, first introduced by
Roberts, the time axis at the satellite is divided
into equally spaced intervals called time slots
which hold a single packet [133. Under the
Slotted Aloha regime, packet an only be
transmitted startin& at the beinning of a slot.
For fixed length packets and PoXseen traffic
arrivals, the capacity of the slotted system is
twice that of the unslotted system due to the
reduced number of collisions at light traffic
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OO3
loads, In oth the slotted and the nslotted
ease, Ome form of stability cntrol is eeded
(1,15]. For efficient use of a packet satellite
channel, where the cne-way-ranslt time is much
of satellite channel allooatlon strategy i
appropriate [ 1O]. A priomlty oriented demand
s].1oea%lon of oafcity and ls orently In aily
use In STNET
tb simulation and analysis were used extensively
d effectively in vestigai ese mnd other
cbnel access sches. -ve, thim r s
able to deal effectively on a purely theoretical
associated with develoent of e tecnnoloEy.
Access to an exrentl system s essential to
address topics such as fault etection and
iolation, system stat monitorln and debin&,
terfacl to terretri netr and atewas,
ftware structure d rfoanoe. It was
feasible to oarr out a test of the tecnnolo&y on
e of several existin stellites a it apare
as if exlstl grod stations could be ed  a
cet mode of operation th only
mifications to provide external on/off control
of the carrier by a prorable satellite
processor at each earth station. e cket
satellite technology s also seen as a
tentlally useful lon& term adjunct to exittin&
netrk tecnolo6y for lon ha applications
vclvint oonfarencin&, mti-destiation
broadcasting d escially to provide
connectivity between a lar&e nr of sites (each
with low duty cycle traffic) usin& a 11
fraction of %he leased channel banddth that a
fully co.acted actwork of polut-to-t olrouits
uld have required-
In the 1973-1g? te frame, the only viable
choices for such a test (fr the U.S. point of
view) were the Intelsat satellites, the NASA
rental satellite and one of the several
military satellites. The Intelsat syat s
preferred choice for this activity ecae It
uld be made available most easily and had the
tential for supporting the reultl tecology
on s ceial basis upon cpetlon, if it
proved to be econic. The military satellites
re less appropriate ohoices as tere s not yet
a stated requirement for cket satelll service
in the military. At$.te, international
terest in packet switCi s growi
significantly, and ssible requirements for
interconnection of domestic cket networks in the
different co.tries were identified. In 197B, %he
PANET ad Just been extended to orway and the
U.K., and expertentel use of the APANET was
provint to e quite worthile for resesrc
purposes.
is is the context in which the subect of an
exrental prr on cket satellite
tecbnolo6y was first raised with the British PoSt
office, with the Communications tellite
rration (Comsat), and subsequently with
Norwegian Telecommunication Administration (NTA)
-end .Noulan Defense eaearch Stablisment
,,(DBE)...Jm the follong section,
preparations for te SAET exrent arc
tlin al with the approval proess icb s
2. Preparln for te SET rent
In 97, &he U.E.-Poa Office ree o support
the SATNET exrent by contributing the O.K.
half of te satellite link and by providing access
 the necessary eart.mtalon eqent in
gland. A progrle mtelltte processor was
installed ab te Goonhilly earth station and
ected back tca Eatery at the ARPANET node on
te praises of University 11ege ndon (OCL)
with a 8 Kbps oicatlon line. UCL was
prepared to accept the main research
resnsiility for the O.K. prticipation l te
SATNET progr, an subsequently di o.
Also in 197, sat agreed to U.S. participation
In suc  expertentel activity, ut only if
We carried out under te auspices of one of the
several U.. International Record arriers (IRCs)
icb historically have played the le of
inteediary in ringlng lnternatin data
services to the end customer. omsat is the U.S.
presentative to Intelsat. en te SATNET
project was bei formulated, Comsat also operated
otb the space segment er contract to Intelsat
d the .S. earth stations for the conrti of
U.S. oers. Intelsat itself now orates
space segment.
The only generic classes of service wlch could be
offered by Comsat were those specifically approved
(tariffed) by Intelsat. Clearly, e cket
satellite service was not onE the. After
rlod of iscussion within telsat lasting
saver monts, an Intelsat tariff for a
multi-station service was approved In late t97.
e SA progr was initiated in ptber 1975
with one Intelsat stdar A ( meters) earth
station at Eta, West Virginia and a silar one
at Gnbilly s, gland. Within Noy, the
interactions wit the NTA were handled entirely by
te Norwegian fense esearcb Estblisent.
ile Norgtan partiolpation In the SATN
progr had started with the first meeting of
searchers In 1975, their active rticipation on
the channel began  late 1977 usi the Nordic
earth station at Tan, Sweden. Shortly
tereafter, msat Laboratories mae preparstlons
to rtlcipate actively with a small nattendeO
rtb Terminal (ET) at larksburg, ryland for
system diandais and evaltion. e PET differed
fr the three standarO A earth stations In that
it bad only a 10 meter antenna and could only
ceive at 16 Kilobits/second lle the other
stations could receive at 6 Kilobits/second. All
four stations can transmit at 6 Kiloite/second,
but the large stations must duce their
transmission rate to 16 Kilobits/second to talk to
te T.
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The technical aspects of the SATNET experiment are
not addressed in this paper. Other companion
papers address both system level and experimental
aspects of the program ['19,20,2]. In the
remainder of this paper, the relevant tariff
considerstigma will be diacused and two key
architectural issues will also be considered.
3. Intelsat Tariffs
The new Intelsat tariff which was approved in late
1974 was for a new kind of service known as
Multi-Destination Half-Duplex (MDHD). Simply
stated, MDHD allows one r more members of
Intelsat to Jointly share a eon channel on any
of the Intelsat Satellites for a modest MOHD
payment to Intelsat. The normal leased service
offerings from Intelsat to its members are a
point-to-point service between two earth stations
and a broadcast Service from one prospecified (but
fixed) earth station to at least two others. The
point-to-point service can be either half-duplex
(one way) or full-duplex (two-way). The broadcast
service utilizes only one channel, as a reverse
path is not included.
The MDND capability may be viewed as an extension
of the broadcast service %o allow moe than one
prospecified earth station to transmit. MDHD
allows all participating earth stations to
transmit using their own channel access protocol '
to resolve contentions.
To any member country already participating in an
MDHD service, the added cost is nominally zero
allow additional earth stations to share the MDHD
channel. This assumes that capacity limitations
'are not exceeded and that coordination among a
larger number of sites costs the same. Mwever, a
payment must be made to Intelsat by each member
country which chooses to Join (share) an existing
FHD channel, so the total payment received by
Intelsat for MDHD service grows linearly with the
number of countries. The easons for a choice of
tariff in which the cost per country is
independent of the number of participants depends,
in part, upon the olitical structure of Intelsat.
The subject of PTT tariffs to the end customer,
although not specifically discussed in this paper,
would generally include earth station
terrestrial charges, as well as space segment
charges.
If we assume Intelsat'normally charges amember C
per one-way channel of a certain capacity for a
total of 2C counting bth ends, then the same
revenue would be gathered if each of the
participating members in an HD channel wre
charged 2C/N apiece (assuming N participants).
The members, in turn, could base charges to their
customers on these costs plus the added costs of
ground station euipment and terrestrial
interconnection. This kind of formals in which
the space segment charge is independent of the
number Of earth stations appears well-suited to
domestic services where all the earth stations are
owned by one authority. However, this formula
poses several problems when applied to the
,international situation,.where the earth stations
are separately owned and operated.
First, the eats ase ½r aeh participating
ountry ould fluctuate as ß function of the
number of participating countrieS, making
fi&ncial management nd planning awkward and
unpPedictable at est. .Second and mute
imprant, .le voing rights f eaah member
country in Intelsat are a function of its total
ayments to Intelsat. Primarily, for that rason,
the Intelsat Mp tariff ws fixed to be a
costant ½ per channel per country.
Te Intelsat broadcast tariff illustrated in Fig.
1(a) shows one transmitter which is charged C and
four receivers each of which is charged C/2 for a
total of 3C. Since at least two receivers oust be
present for a broadcast service, the minimum.
charge is ZC (wich is identical to the half
duplex in-to-plnt tariff between two
The revenue produced by the broadcast tariff
increases linearly with the addition of more
ground stations at an increment of C/ per added
receiving station.
The MDND tariff illustratcd in Fig. l(b) shows
each participating country being charged C for the
right to receive add transmit on the same channel.
The net payment to Intelsat, 5C, is almost double
the charge for the smple broadcast case.
However, the value received for this added cost is
full N-way cOnneCtivity since anX of the earth
stations can transmit to the others at anF time
according to the chosen channel access protocols.
The MDHD tariff is also considerably cheaper than
that for N distinct broadcast channels to
implement N-way connectivity (NC va. INC 
N(N-1)C/2]). Along with the initial hiher cost
of N boadcast channels would nome N tes the
capacity, however, eEardless of wether It ess be
ud effeotively or not.
With these existing tariffs, the cost per country
normalized by total number of channels of network
capacity available o the N earth stations is C
for the I'HP case and [C + (N-1)C/]/N = (N+lJC/2
for the case of N broadcast channels. If existing
MDHD tariffs are extended to channels wit a
higher bandwidth using a 'linear extrapolation" of
the current tariff, the charges for obtaining the
added capacity with multiple lower capacity
broadcast channels will be half as much as the
single MDHD channel as the number of participating
earth stations becomes large. Since this ratio
eflects only the current tariff structure, the
ratio could be changed (e.g., becoe closer to
unity) with a non-linear tariff revision
applicable to higher bandwidth channels.
From an architectural point of view, the use of
multiple roadcast channels has both positive and
negative features which are identified in section
6. However, in most applications, it is doubtful
whether initial network-wide traffic will be large
004
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005
enough tc justify commencing service with more
than a single MDD channel.
4. COMSAT and IRC Filings in the
The U.S., U.K. and Norway participation
has been on an experimental basis and a service
has not yet been offered to Customer in any of
eae countries. In the U.S., aa filed a
rff with the FOC in 1975 %o offer -
exrimental acke% atelllte cability
 its desinateO =oatmatters via one of the
ICs. The service sat offend was based On the
 servie obtaln fr Intelsat, d
aented as requid with the DroErable
satellite pocessor at the eart s%ion. In its
filing, sa also eferred to its
service as HD.
sat bought or leased all te necessary Kroud
tation equileat to provide the exrental
service as for a nodal oeroisl
offering. In a competitive selection, Western
Union International (WUI) was cnose b the
service to the ARA proEr. WUI, in tn, filed
obtained fr Comsat, which they amented witD a
terrestrial circuit before supplying it 5o the
6over. eat.
goVeret's request for proposals was umual in
that it did not dire any specific destination or
custe location ahead. Rather, 1% sply asked
for  HD channel from the U.S. o an
pecified int in the U.K. and sated taC all
of the U.K. costs re to  as$ed by the
British Pot Off lea. A lnt of contact In
Post Office was identified. e request also
stated that additional mpecified destinations
mh% ave to e connected subsequently, as Nervy
eventually was.
To validate te initial delivery of the service
and to verify meatoral of service in he event
outage, only a loopback test fr the
cuzter site (ich was speclfle to  the
iic Data alysis nter tn Alexandria,
Virginia) to he satellite and ack wa require.
The paten% to WUI was not cndent on the
partioilon (or rfoanae) of y other
co.try (or its equ..owver, the  and
COIAT tariffs both included a small charge
ortional to the nr of participating sites
for cochinatica.
A diar of the HD paent flow during the
experiment Is sho in Fi. .
5. SATET rent
The SATNET ent was conducted nlnally
dui the period from ptemr 1975 through
ptember 1978 and involved researchers fr each
of the three rticiti countries. The basic
physical architecture of SAET was dictated by
many programmatic considerations (e.g. ue of
existing ground stations and satellites) so the
actual hardware configuration merely reflects what
%rag available for use in the experiment. However,
tDe logical architecture of the system has been a
auJeot for research and bas constantly evolved
during the coUrse of the program. Neither the
software architecture nor the system protocols
were prescribed in advance and the aSh-hardware
parts of the system interfaces were also allowed
to evolve, which they did. Each was e major
subject for investigation and exploratory
development during te CoLirma Of the project. The
resulting logical architecture wll be ¾ery useful
in designing a more advanced follow-on system. In
addition, an effort ws undertakem to develop and
demonstrate a high prformance digital burst modem
and error control unit for possible operational
use wit SATNET after the experiment.
A major decision in the program was to separate
the SATNET development and testing from the
closely related internerring research activities
which were Just getting underway. It was decided
to pursue the internerring research using a
separate minicomputer gateway in each country
simultaneously connected as a Host on SATNET and
as a Host on the Arpanet [22,23]. This
arrangement left enough flexibility to pursue
gateway related research without resulting
software changes (in rel~time) to SATNET or
Arpanet. The gateway software could have been
incorporated within the physical confines of
either SATNET or Arpanet, or split between them.
owever, keeping it separate for the purposes of
the experimental program provided maximum
flexibility to the internettln s researchers, many
of whom were also working on SATNET, Arpanet or
other ongoin networ related pro, rams without
unnecessarily distracting those SATNET researchers
who did not need to be deeply involved in the
internerring work at that time.
Technical direction of the program beginning in
September 1975 was the responsibility of Linksbit
Corporation, San Diego, allfornia who prepared a
comprehensive test plan to guide the conduct
the experimental program. Major participants were
CO. sat, Bolt Beranek and Newman, University of
California at Los Angeles (UCLA) and the Defense
Communications Agency in the U.S., University
College LOndon and the Post Office in the
and NDRE and NTA in Norway.
Coordinating a program involving participants fro
multiple countries as an important challenge that
was met at several different levels. Ouarterly
review meetings were held (otated among the
different locations) and attended by all the
participants. Technical progress was reviewed at
these meetin&s, technical issues were discussed
and resolved and plans for each succeeding usrter
were refined. Research issues end results were
docented and circulated in a series of informal
working group notes. The ARPANET played a
particularly important role in executing the
effort as well as in coordinating it. It provided
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006
ira means by which %he satellite processors were
down-line loaded and debugged, and the meas by
aich SATNET itself was cTtolled and monitored
as i% was being developed. The message pasir
capability of the bo3ts on the ARPANET were used
to keep all participants informed of technical
progress, system status, often by direct reporting
from tl%e programmable satellite processors in
SATNET, and to resolve questions and culminate
experiments on a day-by-ay basis. Without much a
capability, it is doubtful that the overall
experimental program could have been carried out
successfully.
The main results of the exriment are bainõ
documented by Linksbit Corporation (with inputs
frm all the participants) in a final report to be
available shortlyl A Smmary of the findings show
that the SATNET experiment demonstrated the
feasibility of the packet satellite technology,
llluminaed many of the most iportant technical
and non-technical issues and provided a system
that can support advanced co-purer comunication
research applications. lthouh the subject of
packet voie has not been emphasized in this
article, it played an integral ole in the SATET
design. SATNET is the only operatin lone haul
packet switched network in the world that has been
demigned to handle both packet switched voice and
data.
6. Architectural Issues
Two architectural issues arose durin the Course
of %his project which are appropriate to single
out for mention. The first issue is selecting the
functionality that ought to reside in the
proccssor which is cOldCared with the rest of the
earth station equipment and the functionality that
ought to reside at the terrestrial interface {to
the earth station) which might be located some
distance from it. The second major issue concerns
the means of increasing the overall traffic
handlin E capacity of the system. Each of these
issues are briefly mentioned below.
a. Functionality of the Earth Station and its
Terrestrial Interface
Although not all the functions mplemented in
SATNET need to resi__-.h earth station, a
minimu set of functions must be located there to
control timin and access to (and transmission on)
the satellite channel. Barts of the functionality
might he moved to a terrestrial location distant
from, but connected to, the earth statio by a
communication line. One attempt at the definition
of the functionality is iven in [2]. In
particular, certain aspects of the functionality
which deal with multiplexE traffic r many
'uers into a comslte stream to the earth station
could proably be relocated without penalty in
erformance provided delay or unrelitbility is not
added outside the earth station. Accountin and
other administrative functions could also be
remo%ed from the earth station without penalty.
b. Expansion of Network Capacity
Although a single 64 Kilobits/second channel is
:learl uld be nufficient for many
applications. The capacity of a SATNET system
could be expanded l several ways. First, it
could be simply scaled up in data ate. The
ability of s packet switch to handle.
ultl-eabit/econd data as been demonstrated
[]. Ibis would suffice for an expansion of one
or two orders of mEnitude. A transponder can
typically handle upwards of 6 4eEbits/second ,
however, nd the newer smtellite systems are
epected to support higher data rates still.
Multi-Droeemsor systems see capable of supportin
these hi,her data rates on a single shared
satellite channel without either increased delay
in bufferin or processir. owever, the number
of processors must grow linearly With capacity and
special attention must be paid to communication
between processors and with external devices.
A second alternative, whic baches attractive
wen the overall netrk traffic is high enough,
is to corpoate dedicated upliks using
Frequency Dlvfslon Multiple Access (FA).
this scheme, which is illustrate  FiE. 3, a
separate Drocesso at each eart station uld
dolink and would pa=s alons %o a concenta%or
only hose packets elned fo i earth
Te capaelty of the concenao ould %hen be
sized  he thoushpu inSended fo ha site
wlch 6sably d be h les than th total
network traffic. In this scheme, a mification
would be required at each exlatin E Eund station
fo each new addition to the net, which is a ma3om
isadantage. However, it s highly modular and
shoed be easy to upErmde in an orational
system.
The use of multiple FA broadcast channels, one
per site, reUuoes the earth ttion prccessinE
requirements but it also does not provide the
flexibility that comes from the dyaic
of pacity in a MA system. A thir alternative
is a hybrid of cases one a two above in which
e of the uplin may be BD channels (using
TA) ile the rest may be badcast channels
each from a sidle source.
7- Future Plans
SATNET currently sees as the backbone for a
r of innovative research applications d has
bece the prima packet transrtation vehicle
ten the U.S. and rope for cputer
lcations and command and control research.
SinCe  1979, AANET access fr the U.K. has
r lmost exclusively via SA on a provisional
sis. It Is planned to continue the use of
SATNET as the primary link between ARPA end its
search partners in rope. e ARPAN link
London (via Norway) is scheduled to be taken
during the last quarter of 1979 aer which
only available ARPANET access fr the U.K. will
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 007
b via SATNET. NDHE will utilize SATNET for
research purposes; %he only planned use of the
rmanir pOin-to-point ARPANT link fro the
U.S. to Norway will be foletrieval of seismic
data, which was the o/6inal function of that linc
prior bo its incorporation in the ARPANST in 1973.
WithiD the U.S., ARPA plans %0 use the SATNET
satelite =hannel operatir a 3 Mbps with 5
anteana initially at Lincoln Laboratory,. i
xtton, saachuetts d USC/ISI in rina
ey, Califomma. AdditOn sites In the n
Fansieo aea and Washi.tun, D.C. aea will
also be adoe. A o uae fo %he
channel is o exploe ne use. of the ATNET
techn01oy %o supp% mul:i-use lnte6ated packet
voice nd Oatm emlCation. ly with the
increseed anwidth will a test of this concept
ssile usin multiple aee an dea sources
including a mix oF 2.4 Kilobits/second to 64
facsimile and nodal cpu%e %o upu%eF
The fense iationa eny also plans
utilize tRis tecolosy alon with ARPA for
advanced re.arch and develoet on D
tegrated sta/voice networks of the ture.
 the international soene, packet satellite
technology may be ueful fo a wie variety of
ten%ial applications. e such possibility
ich is bein E offered as a seviee by the
and the US Postal Sewlee is Intelst. This
an innovative new facsile service ich is
Dlan evolve, inividual point-to-point links
oory. A cke stelite y could support
=he initial Intelpot raffie %h oly oe shaed
channel, wit consideal less oal aellic
owidh th multiple point-tit link would
quie and without noticeable de6radaion of
Acowledmenta
Tis effort would not have been ssible without
e eooera%on and support of e BPiih
Office an the Norwegian Teleeiatlons
Admiustration;'  orgai:ios layed a ery
central le In he Drr. lt ranek &
Nean (RtN), COMSAT, an LinCbit rporation
played signifil,mr _zz!n evepi th pak
satellite technology. CT speahesded the
sppval priest. UCL, NDRE, UC, and
with the assistance of BN, caied out the
decDire %he lapse ea9hic distan=es fF SATNET
and each other which might otherwise have been a
deterrent. The success of the progr was due
no mall measure to e technical direction
provided by Linksbit rporation.
He f orenoes
[1] Special Issue on packet Comunications, IEEE
Proceedings, Nov, 1978
[]
I.M. Jacobs etal, "General Purpose Packet
Satellite Networks," IEE Pc., pp. 1418 -
1467, Nov. 1978
[]]
L.O. Roberts and B. U. Wessler, "Computer
Network Development to AChieve ReSource
Sharing," AFIPS Conf. Proc., $JCC, pp.
[]
R.E. Kahn, "Resource Sharing Cxxuputer
Communication Networks," IEEE Poc., pp. 1397
- 107, Nov. 1972
N. Abramson, "The Aloha System - Another
Alternative for Computer Cmunicattons,"
AFIPS Conf. Proc., FJCC, pp. 695 - 70Z, 1970
L.O. Roberts, "Extensions of Packet
Cmunication Technology to a Hand Held
Personal Terminal," AFIPS Conf. roc., S4CC,
Pp. 295 - 29, 1972
[7] R. E. Kahn, "The Organization of Computer
Resources into a Packet Radio Network,"
trans. on Coma., Vol. C0-25, pp. 169 -
Jan. 1977 (also in AFIPS Conf. Proc., NCC,
pp. 177-185, 1975)
[õ] L. Kleinrock and F. Tobagi, "Random ACceSs
Techniques for Data Transmission over Packet
Switched Radio Cannels, AFIPS Conf.
NCC, pp. 187-201, 1975
[9]
R. Binder et al, Aloha PacRet Broadcastin -
A Retrospect," AFIPS Conf. Proc., NCC, pp.
203-2t5, 1975
[10]
N. Abramson and F. Kuo, Editors, Computer
Communication Networks, Prentice Hall,
Englewood Cliffs, N.J,, 1973 (see chaD. on
the Aloha System)
(11]
N. Abramso, "Packet Switching with
Satellites," AFIPS COnF. Proc., NCC, pp.
695-702, 1973
L. Kleinrock and $. S. Lam, "Packet Switchin&
in a Slotted Satellite Channel," AFIPS Conf.
Proc., NC½, p. 703-710, t973
[13]
L. O. Roberts, "Aloha Packet ystem with and
witDuct Slots and Capture," ACM SiCCUFf,
Cxputer Communication Review, Vol 5, No. 2,
April 1975
L. Kleinrock an S.S. tam, "Packet Switchin
iff a Multiaccess Broadcast Channel:
PerformsDee Evaluation," IEE Tran. on
Vol. COM-3, pp. 10-Z3, 975
[15] 5. S. Lam and L. Kleinrock, "Packet Switching
in s Multiaccess Broadcast Channel: Dynamic
------------------------------<page break>-----------------------------
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008
[17]
[22]
[Z53
Control Procedures," IE-E. Trans. on Comm.,
¾ol. C0-23, Sept, 1975
L. C. Roberta, "Dynic Allocation of
Satellite Capacity through Packet
NeaervatiOn," AFIPS Cnf. Proc., NCC,
711-716, 1973
I.M. Jacobs et al, "C-PODA - A Demand
Asignment Protocol for SATNET," Fifth Data
Comunica%ions Symo3ium, Snowbird, Utah,
1977
I.M. Jacobs et al, "Packet Satellite Network
Dsign Issues," Pro. TC, Nov. 1979, in this
Proceedln
P. T. Kirkrein et al, "SATNET Applications
Activities," Proc. NTC, Nov. t979, in this
Poeeedlns
D. A. HoNeill et i, "SATNET Monitoring and
Control," Proo. NTC, Nov. 1979, in this
Proceedings
W.W. Chu et al, "xperimental Remults on the
Packet Satellite Network," Proc. NTC, Nov.
1979, in tbi PrOceedings
V. O. Cerf and R- E. Kahn, "A Protocol for
PacKet Network Interoommunicmtiom," IEEE
Trans. on Comm., Vol. C0-22, pp. 637-64õ,
May 197a
V.O. Cerf and P.T. Kitstein, "Issues in
PacKer NetWork Interconnection," IEEE Proc.,
¾ol 66, No. 11, pp. 1386-1O8, Nov. 197
E.V. Hoversten and H. L. Van Trees,
"International roadoast Packet Satellite
Services," ICCC-?8 Conf. Proe., Kyoto, Japan,
Sept. 1978
$.M. Ornsein et al, "Plurlbum, A Reliable
Multiprocessor," AFIPS Conf. Proc., NCC, pp.
551-560, 1975
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